Introduction

Wetlands are widely recognized as one of the most vulnerable ecosystems to climate change and especially the increased severity of drought (Johnson et al., 2010; Zedler and Kercher, 2005). This is especially true for wetlands in mountainous and alpine areas, where climate change, causing effects such as reduced snow cover, is accelerating (Burkett and Kusler, 2000; Carpenter et al., 1992; Erwin, 2009). However, despite their importance and sensitivity to climate change, the vulnerability of montane wetlands has not yet been quantified, mainly owing to a lack of research. Montane wetlands are refugia and hotspots of biodiversity (Chatterjee et al., 2010; Son et al., 2014) because they have a relatively low species diversity but provide unique habitats for specific species (Omar et al., 2016).

The Wetlands Conservation Act (Ministry of environment, 2021b) defines inland and coastal wetlands as areas where freshwater, brackish water, or saltwater covers the surface permanently or temporarily. According to the topography, inland wetlands are classified as river, lake, or hill types. Hill-type wetlands are divided into those that are high moor, low moor, lowland wetland, and marsh, according to their vegetation, soil, and hydrological regime. These wetlands have the following functions: a hydrological function enabling land moisture regulation through naturally formed drainage and irrigation; a biodiversity maintenance function by providing habitats for various organisms; a carbon storage function, for example, peatlands absorb carbon through the remains of emerged plants and aquatic plants around wetlands while accounting for only 3% of the world's land area but containing approximately 30% of all carbon on land; trapping and fixing sediment with the roots of the plants that make up the wetlands; and moderating damage from disasters such as flooding and storms (Ramsar Convention Secretariat, 2013).

According to the Korea Forest Service, forest wetlands are defined as all wetlands (such as swamps, marshes, and peatlands) that are found in areas classified as forests, as well as swamps that are home to woody plants such as tall trees, shrubs, and bushes, even in those areas not classified as forests (Korea Forest Service, 2006). Over an eight-year period from 2006 to 2014, the first national survey of forest wetlands covered 6.37 million hectares of forests within national and private forest areas. A total of 1,280 forest wetlands were precisely surveyed for five years between 2015 and 2019, which included 1,264 sites derived from the first survey and 16 new target sites. A second survey of forest wetlands was conducted to grade the sites following evaluation. Consequently, 455 sites functioning as forest wetlands were classified by type. There are the total of 455 forest wetlands in Korea, 193 natural forest wetlands, 237 abandoned paddy field forest wetlands, 2 man-made forest wetlands, and 23 modified forest wetlands (Lee et al., 2022b).

On the Korean Peninsula, forest wetlands are a hotspot for biodiversity conservation, and they represent ecosystems that must be protected and managed, but to effectively do this, it is crucial to have a better understanding of their current state.

In addition, measures for effective management of abandoned paddy field type forest wetlands should be urgently sought, and the most effective method is to designate a Forest Genetic Resources Reserve (FGRR) and Other Effective area-based Conservation Measures (OECMs) is a method through designation. Therefore, for this, the most basic investigation of flora and vegetation should be accompanied. The purpose of the present study was to investigate the vascular flora that must be surveyed to conserve and utilize forest wetlands in the long term, as well as to use this information as the basis for the restoration of forest wetlands in preparation for future climate changes.

Materials and Methods

Study area

Abandoned paddy field type forest wetlands account for the largest proportion of 52.1% in 237 places among the four types of forest wetlands. Moreover, out of 455 forest wetlands, 323 private forests accounted for about 71% of the area, and in abandoned paddy field type forest wetlands, 212 out of 237 private forests accounted for about 90% of the total. It is highly likely to be damaged, destroyed or lost due to development, etc. The 237 abandoned paddy field of forest wetlands are distributed across 13 administrative districts, excluding Seoul Metropolitan City, Daejeon Metropolitan City, and Jeju and Sejong Metropolitan Autonomous City (Fig. 1). The region with the greatest number of forest wetlands is Gangwon- do with 72 sites (30.4%) covering an area of 608,725 ㎡ (35.8%), followed by Gyeongsangbuk-do with 44 sites (18.6%) covering an area of 478,458 ㎡ (28.1%) and Jeollanam-do with 29 sites (6.4%) covering an area of 120,302 ㎡ (7.1%).

Fig. 1.

Map showing the location of 237 abandoned paddy field type forest wetlands.

Additionally, 25 sites (10.5%) were state-owned forests while 212 sites (89.5%) were privately owned forests. Altitudes range from 20 m to 1,022 m above sea level. However, 210 forest wetlands (approximately 88.6%), were found to be distributed at elevations below 500 m, 27 (approximately 11.4%) at elevations between 501 m and 1,022 m.

The grade of forest wetlands was evaluated using a 5-point scale according to the evaluation items, and the weight of each item based on the research results conducted by the Korea Forest Service reflected quantitative data surveyed in the field high, and the contents related to the estimate were reflected low. accordingly, vegetation and landscape 40%, material circulation and hydrosluice 40%, Humanities, society, landscape 10%, and degree of disturbance 10%. Scores evaluated for each item are converted into a full scale of 100 points, and after adding up, grades of 71 or higher are graded A, 61-70 points are B grade, 51-60 points are C grade, and 50 or less grades are graded according to the score. The 237 abandoned paddy field forest wetlands were classified into grades A, B, C, and D, with 11, 110, 102, and 14 sites accounting for each grade, respectively (Table 1).

Research method

Field note was used for survey of flora. The field note includes survey number, survey date, investigators, survey site, altitude, survey route, GPS coordinates, according to the order of plant numbers, plant name, image data, and specimen collection items. A field survey of vascular flora was conducted between April 2015 and November 2021. Plant species were identified in the field as much as possible to prevent disturbance to the plants, and in the case of plants that were difficult to identify in the field, only individuals with reproductive organs were collected for laboratory identification. Identifying plants was based on literature from Lee (1996), Lee (2014a; 2014b), and Lee (2006). Taxonomy of the occurring plants was based on Engler's taxonomy (Melchior, 1964), and the list was arranged accordingly (Appendix 1).

These scientific names and Korean names were derived from the Korea National Plant List (Korea National Arboretum, 2022). The plant list was arranged by family, and the classifications of the genera and below taxa were arranged alphabetically. Listing endemic plants followed Chung et al. (2017), endangered wild species followed Ministry of Environment (2021a), rare plants and red list followed Korea National Arboretum (2009) and National Institute of Biological Resources (2021), floristic target plants followed Kim (2000) and National Institute of Ecology (2018), northern lineage plants followed Gantsetseg et al. (2020), and invasive alien species followed Kang et al. (2020). The classification of wetland plants by vascular plant type followed Choung et al. (2012; 2020).

Results

Vascular flora

The vascular plants identified in 237 abandoned paddy field forest wetlands in South Korea belonged to 128 families, 510 genera, 1,022 species, 27 subspecies, 87 varieties, 10 forma, and 1,146 taxa (Table 2). Ferns accounted for 49 taxa, belonging to 14 families, 23 genera, 47 species, and 2 varieties, gymnosperms for 4 families, 9 genera, and 12 species, angiosperms for 1,085 taxa, belonging to 110 families, 478 genera, 963 species, 27 subspecies, 85 varieties, and 10 forma, and monocotyledons for 305 taxa, belonging to 18 families, 123 genera, 277 species, 4 subspecies, 21 varieties, and 3 forma. This accounted for about 24.2% of the 4,724 taxa of vascular plants in Korea (Korea National Arboretum, 2022). The plant families with the highest number of species recorded were Asteraceae (108 taxa, 9.4% of species recorded), Poaceae (105 taxa, 9.1%), Cyperaceae (94 taxa, 8.2% of species recorded), Rosaceae (54 taxa, 4.7% of species recorded), and Fabaceae (47 taxa, 4.1% of species recorded).

The most frequently occurring species were (in descending order): Salix pierotii at 183 sites (77.2%), Persicaria thunbergia at 177 sites (74.7%), Oplismenus undulatifolius at 163 sites (68.8%), Artemisia indica at 145 sites (61.2%), Rosa multiflora at 140 sites (59.1%), Clematis apiifolia at 135 sites (57.0%), Zanthoxylum schinifolium and Impatiens textorii at 132 sites respectively (55.7%), Amphicarpaea bracteata subsp. edgeworthii at 125 sites (52.7%), Equisetum arvense at 122 sites (51.5%), Juncus decipiens and Ligustrum obtusifolium at 120 sites (50.6%), Erigeron annuus at 118 sites (49.8%), Acer tataricum subsp. ginnala at 108 sites (45.6%), Persicaria sagittate at 106 sites (44.7%) and Thelypteris palustris at 102 sites (43.0%) (Fig. 2). However, among the 1,146 taxa, 551 taxa including Ranunculus chinensis were observed at only ten or fewer sites, and 273 taxa including Triadenum japonicum were recorded at only one site.

Fig. 2.

The bar chart showing the status of species appearing in more than 100 survey areas in abandoned paddy field type of Korea's forest wetlands.

Endemic plants of the Korean Peninsula

A total of 43taxa of endemic plants on the Korean Peninsula belonging to 23 families, 37 genera, 39 species, and 4 varieties were identified in 237 abandoned paddy field of forest wetlands (Table 3). This accounts for 11.9% of the 360 taxa of endemic plants of the Korean Peninsula (Chung et al., 2017). In the 237 forest wetlands, the most frequently occurring endemic plants of the Korean Peninsula were and Salix koriyanagi, which were found in 64 sites, followed by Weigela subsessilis occurring in 63 sites, and Clematis trichotoma in 15 sites, Populus ⨉ tomentiglandulosa, in 11 sites, Aster koraiensis in 9 sites and Carex erythrobasis in 8 sites respectively (Fig. 3).

Fig. 3.

The pictures showing Korean endemic plants in abandoned paddy field forest wetlands.

Endangered wild species and Rare plants on the IUCN red list

The term endangered wild species refers to species in danger of extinction in the near future, with a very small number of individuals remaining whose population has been severely reduced by natural or human factors (Ministry of Environment, 2021a). Four taxa were identified as endangered wild species of grade II, such as Eleutherococcus senticosus, Cicuta virosa, Trientalis europaea var. arctica, and Utricularia uliginosa.

A total of 58 taxa were identified as of rare plants on the IUCN red-list, and they belonged to 36 families, 50 genera, 54 species, 1 subspecies, and 3 varieties (Table 4). This is about 10.2% of the 571 taxa on the rare plant list of Republic of Korea (Korea National Arboretum, 2009), which was re-evaluated by the Korea National Arboretum according to the IUCN criteria. 5 taxa Critically Endangered (CR), 4 taxa Endangered (EN), 15 taxa Vulnerable (VU), 23 taxa Least Concern (LC), and 11 taxa Data Deficient (DD) were classified (Table 4, Fig. 4, Fig. 5).

Fig. 4.

The pictures showing rare plants in abandoned paddy field forest wetlands.

Fig. 5.

The map showing rare plants in abandoned paddy field forest wetlands.

Moreover, vascular plants on the National Red List (National Institute of Biological Resources, 2021) were identified as a total of 45 taxa. Critically Endangered (CR) species belonging to the threatened category did not appear, Endangered species (EN: Endangered) in 3 taxa including Actaea heracleifolia, and Vulnerable (VU: Vulnerable) in Carex idzuroei and Eleutherococcus senticosus 2 taxa. confirmed to be 8 taxa including Cicuta virosa were identified as Near Threatened (NT), and 27 taxa including Utricularia caerulea as Least Concern (LC) (Table 4, Fig. 4).

Floristic target plants

A total of 296 taxa were identified as floristic target plants. These belonged to 85 families, 198 genera, 278 species, 4 subspecies, and 14 varieties (Appendix 1, Fig. 6), representing about 25.8% of the 1,146 taxa of emergent plants and 20.1% of the 1,476 taxa of floristic target plants. A total of 7 taxa including Actaea heracleifolia, Cicuta virosa and Utricularia uliginosa were identified, accounting for 2.7% of the 258 taxa belonging to grade V. A total of 38 taxa of grade IV floristic target plants were identified, such as Utricularia caerulea, Utricularia bifida and Carex capricornis. Approximately, 8.6% of the total 440 taxa of grade IV plants was observed in the forest wetlands. And a total of 77 grade III taxa were identified, including Lysimachia vulgaris var. davurica, Betula davurica and Spiraea fritschiana. Approximately, 20.8% of the 371 taxa of grade III floristic target plant taxa were present. A total of 72 taxa and 102 taxa of grade II and I floristic target plants were identified respectively. Approximately, 34.8% of 207 taxa and 51% of 200 taxa of grade II and I each.

Fig. 6.

The pictures showing rare plants in abandoned paddy field forest wetlands.

Invasive alien plants

A total of 86 invasive alien plant taxa were identified, belonging to 36 families, 73 genera, 84 species, and 1 subspecies 1 varieties (Appendix 1). This represented approximately 22.9% of the 375 taxa in the invasive alien plant inventory (Korean National Arboretum, 2019).

The 375 taxa of invasive alien plants in the country were divided into five classes according to the degree of spread: widespread species (WS), serious spread species (SS), concerned spread species (CS), minor spread species (MS), and potential spread species (PS) (Gang et al., 2020). Of these, WS plants are those recorded at 101 sites or more, and 19 (5.1%) of the 375 taxa fall into this category. A total of 17 taxa, including Erigeron annuus and Bidens frondosa, were identified as WS plants during the survey. SS species are those with 75 to 100 distribution sites, and 16 (4.3%) of the 375 taxa fall into this category. A total of 8 taxa were identified as SS in the survey, including Carduus crispus and Symphyotrichum pilosum. CS species are those with 50 to 74 distribution sites, and 19 (5.1%) out of 375 taxa fall under this category. A total of 8 taxa were identified as CS, including Quamoclit angulata and Solidago gigantea. MS species are those with 25 to 49 distribution sites, and 37 (9.8%) of 375 taxa fall into this category. A total of 14 taxa were identified as MS, including Sicyos angulatus and Bromus tectorum. The rate of spread of Sicyos angulatus and Ambrosia trifida is very fast. PS species are those with less than 24 distribution sites, and 284 (75.7%) out of 375 taxa fall into this category, and 5 taxa, including Ageratina altissima and Elymus repens, were identified as PS.

Categorization according to wetland preference of vascular plants

Based on Choung et al. (2020), the plants identified in the survey were assigned to the following categories according to the frequency of appearance: obligate wetland plant (OBW), facultative wetland plant (FACW), facultative plant (FAC), facultative upland plant (FACU), and obligate upland plant (OBU). Consequently, OBW accounted for 79 taxa (6.9%), FACW 103 taxa (9.0%), FAC 61 taxa (5.3%), FACU 66 taxa (5.8%), and OBU 837 taxa (73.0%) (Table 5).

For each category, the plants with the highest occurrence frequency in forest wetlands were examined. For OBW, Phragmites japonicus appeared 96 times, followed by Aneilema keisak 71 times, Isachne globosa 65 times, Phragmites australis 56 times, and Oenanthe javanica 48 times. For FACW, Salix pierotii appeared 183 times, followed by Persicaria thunbergii 175 times, Impatiens textorii 129 times, Juncus decipiens 118 times, and Persicaria sagittata 106 times. For FAC, Carex forficula appeared 66 times, followed by Angelica decursiva 54 times, Glyceria leptolepis 41 times, Hypericum laxum 33 times, and Spiraea salicifolia 28 times. For FACU, Equisetum arvense appeared 120 times, followed by Acer tataricum subsp. ginnala 108 times, Thelypteris palustris 103 times, Pilea pumila 80 times, and Persicaria senticosa 50 times. For OBU, Oplismenus undulatifolius appeared 163 times, followed by Artemisia indica 143 times, Rosa multiflora 140 times, Clematis apiifolia 134 times, and Zanthoxylum schinifolium 131 times.

Distribution of vascular plants by region

The flora of the abandoned paddy field type of forest wetland 237 sites in Korea belonged to 128 families, 510 genera, 1,022 species, 27 subspecies, 87 varieties, and 10 forma, with a total of 1,146 taxa recorded. Among them, the flora of 72 sites in the Gangwon area belonged to 768 taxa (67.0%), including 106 families, 374 genera, 679 species, 21 subspecies, 62 varieties, and 6 forma, and 28 taxa, such as Pilea oligantha, were found to be endemic to the Gangwon area. The flora of forest wetlands in 25 locations in the Gyeonggi region (including Incheon) was identified to consist of 474 taxa (about 41.4%), belonging to 95 families, 272 genera, 421 species, 14 subspecies, 33 varieties, and 6 forma, among which 17 taxa including Carex erythrobasis were found to be endemic to the Gyeonggi area. The flora of the 74 forest wetlands in the Gyeongsang-do belonged to 114 families, 369 genera, 630 species, 23 subspecies, 58 varieties, and 6 forma, with a total of 717 taxa (about 62.6%). Of these, 17 taxa including Polygonatum infundiflorum were surveyed to have appeared in the forest wetlands of the Gyeongsang-do. The flora of the 30 forest wetlands in the Chungcheong region consisted of 569 taxa (about 49.7%) belonging to 102 families, 317 genera, 502 species,15 subspecies, 46 varieties, and 6 forma, and 21 taxa including Fraxinus chiisanensis were endemic to the forest wetlands of the Chungcheong region. A total of 547 taxa (about 47.7%) of 105 families, 315 genera, 485 species, 15 subspecies, 40 varieties, and 7 forma were identified in the flora of 36 forest wetlands in the Jeolla region. In the Jeolla region alone, 18 taxa of endemic plants were identified, including Carex pseudochinensis (Fig. 7).

Fig. 7.

The pictures showing the status of survey area and flora of abandoned paddy field type in Korea's forest wetlands.

Distribution of vascular plants by grade

The 237 abandoned paddy field forest wetlands were classified into grades A, B, C, and D, with 11, 110, 102, and 14 sites accounting for each grade. The flora of grade A of forest wetland 11 sites in Korea belonged to 79 families, 213 genera, 292 species, 12 subspecies, 25 varieties, and 4 forma, with a total of 333 taxa (29.0%) recorded. Also 12 taxa, such as Dicentra spectabilis and Galium trifloriforme, were found to be endemic to the A grade of forest wetlands. Among them, the flora of 110 sites in grade A of forest wetland belonged to 953 taxa (83.1%), including 124 families, 454 genera, 852 species, 20 subspecies, 73 varieties, and 8 forma, and 202 taxa, such as Inula linariifolia and Streptopus ovalis, were found to be endemic to the B grade of abandoned paddy field in Korea’s forest wetlands. The flora of forest wetlands in 102 sites in grade C of forest wetlands was identified to consist of 882 taxa (about 77.0%), belonging to 113 families, 423 genera, 782 species, 24 subspecies, 68 varieties, and 8 forma, among which 141 taxa including Galearis cyclochila and Vicia chosenensis were found to be endemic to grade C area. The flora of the 14 D grade forest wetlands belonged to 91 families, 240 genera, 359 species, 13 subspecies, 25 varieties, and 2 forma, with a total of 399 taxa (about 34.8%). and 11 taxa including Calamagrostis pseudophragmites were endemic to the forest wetlands of the D grade.

Discussion

Plant distribution characteristics of abandoned paddy field forest wetlands

The most frequently appearing endemic plants in the abandoned paddy field of 237 forest wetlands were Salix koriyanagi and Weigela subsessilis, which appeared in 64 and 63 wetlands respectively. Wetlands with the most frequent occurrence of endemic plants were Jeollanam-do 2016-27 (Muan-gun Geumjeong-myeon), and Chungcheongbuk-do 2017-14 (Okcheon-gun Iwon-myeon), with eight taxa recorded in each region. In Jeollanam-do 2016-27, Scrophularia koraiensis, Thalictrum actaeifolium var. brevistylum, Weigela subsessilis, Cirsium setidens, Chrysosplenium barbatum, Salix koriyanagi, Scutellaria insignis, and Lysimachia coreana were recorded, and in Chungcheongbuk-do 2017-14, Cirsium setidens, Stewartia koreana, Fraxinus chiisanensis, Weigela subsessilis, Viola seoulensis, Thalictrum actaeifolium var. brevistylum, Aconitum pseudolaeve, and Carex erythrobasis were recorded.

The wetlands where the greatest number of rare plants were identified were in Chungcheongbuk-do 2017-21, Carex capricornis. (CR), Mimulus tenellus (VU), Iris ensata, Gentiana triflora var. japonica (LC), and Eleutherococcus divaricatus var. chiisanensis, Polygonatum infundiflorum, Rumex longifolius (DD) were found. Following by Gangwon-do 2019-26, a total of 6 taxa appeared: Galearis cyclochila (VU), Iris ensata, Gentiana triflora var. japonica, and Lysimachia coreana (LC), Scrophularia koraiensis, and Eleutherococcus divaricatus var. chiisanensis (DD).Analysis of the distribution characteristics of the rare plants by region showed that Eriophorum gracile classified as CR appeared only in only one forest wetland in Gyeongsangnam-do, and Cicuta virosa appeared only in 2 forest wetlands in Gangwon-do, although there was no altitude restriction. Utricularia uliginosa appeared only in the southern regions of Gyeongsang-do. Magnolia kobus appeared only one in the forest wetland of Gangwon-do Gangneung-si, which were located. However, it is thought to have been planted under the influence of previously cultivatied site, and the nearby Royal Tomb of King Myeongjugun.

As wetlands with high OBW occurrence rates relative to the occurrence of 30%, a forest wetland site in Gyeongsangnam-do showed the presence of OBW: Gyeongnam 2015-46. In Daugu 2017-02, 13 taxa were identified: Eriocaulon cinereum, Lobelia sessilifolia, and so forth. And 6 forest wetlands where OBW appeared more than 20% were identified, Gyeonggi 2019 – 37 (29%), Busan 2015-01 (28.1%), Ulsan 2015-11 (24.1%), Daegu 2017-02 (23.2%), Gyeonggi 2019-28 (20.6%), and Gyeongbuk 2017-36 (20.4%) in order. In contrast, there were 4 wetlands with high OBU occurrence rates relative to the occurrence rates of other species sites, where only OBU were recorded: Gyeongsangnam-do 2015- 38 (36 taxa), Gyeongsangbuk-do 2018-07 (24 taxa), Jeollanam- do 2016-05 (14 taxa), and Chungcheongnam-do 2016-19 (47 taxa). And 50 forest wetlands where OBU appeared more than 80% were identified, Gyeongbuk 2017 – 32 (97.4%), Chungbuk 2017-15 (96.2%), Jeonbuk 2016-28 (25.8%), Jeonbuk 2016-27 (95.3%), Gyeongbuk 2017-04 (94.4%), Gangwon 2018-32 (91.7%), and Gyeongnam 2015-21 and 2015-37 (90%) in order. These forest wetlands were located at altitudes of up to 500 m above sea level, which made them highly accessible, and they are considered to be wetlands that are undergoing terrestrialization and losing their function as forest wetlands.

Meteorological data such as average temperature for each region from 1991 to 2020 were reviewed (Table 6). The average temperature ranged from 10.8°C to 13.3°C, and the average maximum and minimum temperatures were 18.7°C and 5.9°C, respectively. The average rainfall ranged from 1,267 ㎜ to 1,377.1 ㎜, showing a difference of about 100 ㎜ between regions. And the average humidity ranged from 65.7% to 71% (Korea Meteorological Administration, 2022).

Looking at the species that appeared in each area of the abandoned paddy field type of forest wetland, 136 taxa such as Pilea oligantha in Gangwon area, 26 taxa such as Clematis brachyura in Gyeonggi area, 89 taxa such as Utricularia uliginosa in Gyeongsang-do, 47 taxa Carex capricornis in Chungcheong area, and 67 taxa including Coreanomecon hylomeconoides were identified in Jeolla region. Species with different distribution areas were found in the surveyed area, but it is difficult to classify them into regional distribution areas due to the characteristics of the abandoned paddy field type of forest wetland, which is located in a mountainous area and has many private forests. Therefore, it is necessary to build an florisitc inventory for each target site and systematically manage it.

In the first forest wetland survey conducted from 2006 to 2014, a total of 1,246 taxa were identified (Korea National Arboretum, 2016). Flora that appeared in this survey were identified as 1,146 taxa in total, and the total flora of both surveys was identified as 1,488 taxa. Among them, 904 taxa including Persicaria thunbergii appeared in the both two surveys, and 342 taxa including Mankyua chejuensis appeared in the first forest wetland survey. This is thought to be the reason why there is no abandoned paddy field type of forest wetland in Jeju and many cultivated plants have been deleted. The newly emerged species in this survey are 242 taxa, such as Sicyos angulatus and Symphytum officinale, and countermeasures against invasive alien plants should be prepared as soon as possible.

Forest wetland conservation plan

The notable plants recorded in the 237 abandoned paddy field of forest wetlands included 4 taxa of grade II endangered wild plants, 185 taxa of northern plants in the Korean Peninsula, 45 taxa of endemic plants of the Korean Peninsula, 59 taxa of IUCN-designated rare plants, and 297 taxa of floristic target plants. In forest wetlands where eight taxa of native endangered wild plants (grade II) occur (Utricularia uliginosa, Cicuta virosa, Trientalis europaea, and Eleutherococcus senticosus), if it is necessary to designate the area as a conservation area through an immediate review of its feasibility or to establish a conservation plan by installing information boards and training local observers. In forest wetlands where native rare plants classified as VU, EN, and CR occur, 1-14 forest wetlands should be designated by Korea Forest Service as Forest Genetic Resources Reserves (FGRR) and other effective area-based conservation measures (OECMs) to be monitored for a cycle of three years (Lee et al., 2022a). For 197 taxa of floristic target plants of grade III and above, precise monitoring around the native habitat should be conducted periodically. OECMs does not involve designating conservation areas but is defined as the management of geographically limited areas over long periods, intending to maintain positive and sustainable in situ conservation of biodiversity, along with relevant ecosystem functions and services, and cultural, spiritual, socio-economic, and other locally relevant values (Convention on Biological Diversity, 2018).

A total of 86 invasive alien plant taxa were identified in 237 forest wetlands by abandoned paddy field type. The species with the highest frequency of occurrence was Erigeron annuus (117 records), followed by Bidens frondosa (87 records), Robinia pseudoacacia (66 records), Oxalis corniculata (41 records), and Phytolacca americana (35 records). Erigeron annuus was identified at 42 (56.8%) of the 74 sites in the Gyeongsang-do, but it was recorded most frequently in the Chungcheong region, occurring at 18 (60%) of the 30 sites. In the Gangwon-do region, it appeared at 35 (48.6%) of the 72 sites, 11 (44%) of the 25 sites in the Gyeonggi-do region, and 11 (30.6%) of the 36 sites in the Jeolla-do region. Erigeron annuus was mostly observed around Gyeongsangbuk-do, Chungcheongnam-do, Chungcheongbuk-do, Gyeonggi- do, and Gangwon-do. Bidens frondosa as a widespread species had a similar distribution pattern. It was found in 12 (48%) of 30 sites in the Gyeonggi region and in 34 (46%) of 74 sites in the Gyeongsang-do and 28 sites (38.9%) in the Gangwon-do region. Robinia pseudoacacia was found in Chungcheong (43.3%), Gyeonggi (32%), Gangwon (25%), and Gyeongsang- do (24.3%). Robinia pseudoacacia is an OBU that often appears at the boundaries of forest wetlands. As it is known not to spread into the interior of forest wetlands, it can serve as an indicator plant for changes in the size of forest wetland areas. On the other hand, Sicyos angulatus (FACW) was recorded in one location in Gangwon 2019-36 area during the second survey of forest wetlands conducted from 2015 to 2021, but its spreading speed is very fast, and it is necessary to pre-empt its spread through monitoring and control measures.

According to Lee et al. (2022b), among abandoned paddy field type of 237 forest wetlands, 14 of grade D were classified as deformed wetlands due to natural disasters and terrestrialization; 212 sites (approximately 89.4%) are privately owned and difficult to manage. Additionally, only 14.3% (34 sites) are currently designated as forest genetic resource conservation areas (Korea National Arboretum, 2016). Therefore, further designation of FGRRs and OECMs will be required. In South Korea, 7 areas of use including National Arboretum, forest wetlands and algific talus slopes were reported to be suitable for OECMs. Therefore, it is necessary to pre- emptively designate 121 (A and B grades) of the remaining 203 sites as FGRRs and apply OECMs and to seek an integrated management plan with systematic and regular monitoring under the administration of government agencies.

Appendix